Simultaneous Determination of Seventeen Quinolones in Aquaculture Seawater Using Solid-Phase Extraction and Liquid Chromatography Tandem Mass Spectrometry

Abstract:

In this study, we developed a method to determine 17 kinds of quinolones residues in aquaculture seawater by using solid-phase extraction and liquid chromatography tandem mass spectrometry (SPE-LC/MS/MS). The target antibiotics in water samples were enriched and cleaned-up by solid-phase extraction cartridges after the acidification with hydrochloric acid. We compared the sample recovery under different conditions to find the optimal pH of the loading buffer and the most suitable type and volume of the eluent. The elute was collected and concentrated under a gentle stream of nitrogen gas, and then dissolved into 1 ml liquid by the mobile phase. All antibiotics were separated by gradient elution with the mobile phase of 0.1% formic acid in water and acetonitrile. The targets were then analyzed by LC-MS/MS under the positive electrospray ionization condition in the multiple-reaction-monitoring (MRM) mode. Seventeen kinds of antibiotics can be separated successfully within 10 minutes. Calibration curves for antibiotics exhibited good linearity in the concentration range from 1 to 200 ng/ml and the correlation coefficients were larger than 0.999. The limits of detection (LOD) were 2-10 ng/L and the limits of quantification (LOQ) were 5-20 ng/L. The average recoveries of 17 quinolones at the spiked concentrations of 20 ng/L, 100 ng/L and 200 ng/L were 71.3% to 125.0% with a relative standard deviation (RSD, n=5) of 2.44% to 12.27%. This new method was applied to the analysis of four mariculture farms located in the Lingshan Bay of Qingdao in China. The results showed that four kinds of quinolones were detected including enrofloxacin, ofloxacin, norfloxacin and ciprofloxacin, and the highest concentration was 6880.05 ng/L. These results suggested that the new method was efficient and reliable, which was suitable for the detection of quinolones in seawater samples.